Stair holding device for vacuum cleaner

ABSTRACT

A mechanism for holding a canister or tank-type vacuum cleaner in an upwardly inclined position on a stairway is disclosed. A pendum-like lock crank passes through the lower interior of the housing of the cleaner and has a pair of downwardly bent locking arms extending outside of the housing. A resilient protrusion is mounted on the bottom of the housing. When the lowermost portion of the lock crank is rotated forward of this protrusion, the mechanism is retained in a disengaged position. When the lowermost portion of the lock crank is rotated rearward of the protrusion, the pendulum action of the lock crank positions the locking arms in contact with the rear wheels of the cleaner such that they can engage so as to lock the vacuum cleaner on the stairway when the front end of the cleaner is at a higher level than the rear end.

United States Patent [191 Brunning et a1.

[ June 28, 1974 STAIR HOLDING DEVICE FOR VACUUM CLEANER Inventors: Elmer Eugene Brunning, Normal;

Donald P. Grover, Naperville; Manfred Schild, Berwyn; Robert William Nickelson, Elk Grove Village, all of I11.

Assignee: Sunbeam Corporation, Chicago, Ill.

Filed: May 14, 1973 Appl. No.: 359,712

US. Cl. 280/80 R, 15/327 R, 188/29 Int. Cl B62d 21/00, B60t 1/04 Field of Search..'...... 280/80; 188/29, 190, 192;

References Cited UNITED STATES PATENTS 1/1962 Descarries 15/327 R 1/1967 Lull 188/29 10/1970 Stanfield 188/29 Primary Examiner--Roben R. Song Attorney, Agent, or Firm-George R. Clark; Neil M.

, Rose; John S. Pacocha [5 7] ABSTRACT A mechanism for holding a canister or tank-type vacuum cleaner in an upwardly inclined position on a stairway is disclosed. A pendum-like lock crank passes through the lower interior of the housing of the cleaner and has a pair of downwardly bent locking arms extending outside of the housing. A resilient protrusion is mounted on the bottom of the housing. When the lowermost portion of the lock crank is rotated forward of this protrusion, the mechanism is retained in a disengaged position. When the lowermost portion of the lock crank is rotated rearward of the protrusion, the pendulum action of the lock crank positions the locking arms in contact with the rear wheels of the cleaner such that they can engage so as to lock the vacuum cleaner on the stairway when the front end of the cleaner is at a higher level than the rear end.

16 Claims, 3 Drawing Figures STAIR HOLDING DEVICE FOR VACUUM CLEANER BACKGROUND OF THE INVENTION The present invention relates, in general, to a mechanism for holding vacuum cleaners, on a stairway in an inclined position and more particularly, relates to a locking mechanism of the type described which may be either selectively disengaged or selectively put into a state whereby the mechanism will be automatically engaged to prevent a rearward movement but allowing forward movement whenever the longitudinal axis of the vacuum cleaneris inclined with respect to the horizontal.

When a vacuum cleaner is to be used on the stairs, the operation of the cleaner is inconvenient, and may even become dangerous, due to the tendency of the vacuum cleaner to fall down the stairs. Thus, in addition to possible damage to the stairway or to the vacuum cleaner, there is always the possibility of danger or injury to the operator or to another person. It, therefore, would be desirable if the wheels of the vacuum cleaner could be quickly and efficiently locked on the stairway so that the vacuum cleaner could not roll backward down the stairs during use. A feature such as this, however, must be provided at a minimum of cost the cleaner is raised, such as would occur when'the operator does not intend to clean the stairs but merely wants to pull the vacuum cleaner up the stairs for use in upstairs room or hall. Another desirable feature would be to have the capability of totally disengaging the wheel lock mechanism such as to allow free mobility even on an incline in both the forward and rearward directions.

Various locking mechanisms are known for vacuum 7 cleaners, but they do not fulfill the desired objectives noted above. Examples of prior devices may be found in the Descarris US. Pat. No. 3,015,123, patented Jan. 2, 1962. The wheeled undercarriage of the vacuum cleaner of the Descarris Patent is complicated and bears little resemblance to the stair holding mechanism It is a further object of the present invention to provide a simple mechanism for locking the wheels of a vacuum cleaner inv an inclined position using a pendulum operating principle.

It is a further object of the present invention to provide an uncomplicated lock crank mechanism which is mounted in holes in the housing of a wheeled vehicle, such as a canister or a tank-type vacuum cleaner, in

which the lock crank mechanism has a pair of downwardly projecting locking arms that engage one or more wheels of the vehicle so as to prevent them from rotating in a rearward direction when the vehicle is positioned on an incline.

Other objects and advantages of the present invention will be apparent to those skilled in the art from the following specification including the drawings and the claims.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall perspective view of a canister type vacuum cleaner which incorporates the stair locking mechanism of the present invention;

FIG. 2 is a rear view of the canister vacuum cleaner of FIG. 1 which shows a partial cut-away sectional view of the lower portion of the vacuum cleaner which illustrates the locking mechanism of the present invention;

TECHNICAL DESCRIPTION OF THE INVENTION A vacuum cleaner suitable for incorporation of the present invention is shown in FIG. 1 and is designated by the general reference number 20. The vacuum cleaner 20 has a front cap 22 and a rear cap 24 which enclose the ends of the elongated canister tank 26..The tank 26 is constructedof two steel shells and soft plastic bumpers 28,. which are preferably extruded of polyvinyl chloride, are mounted on the sides of the tank 26 where the two shells meet to protect furniture. Mounted on the top surface 30 of the tank 26 is a tool holding andhandle assembly 32 and a hose holding wall section 33.,The front cap 22, the rear cap 24 and the tool holding and handle assembly 32 andthe hose holding wall section 33 are all formed of plastic, preferably of a high impact polystyrene. The tool holding and handle assembly 32 consists of a number of upwardly projecting tool holdng posts which support the varioustools and accessories which may be used with the vacuum cleaner such as the wall and floor brush assembly 42, the upholstery tool 44, the crevice tool 46 and the dusting brush 48, respectively. In addition, two metallic wands 50 and 52 may be stored in elongated storage channels 54 and 56 in the rear cap 24, respectively. The operator may then control the movement of the vacuum cleaner 20 without stooping by grasping one or both the wands 50 and 52 so as to direct the vacuum cleaner 20 in the desired direction. If desired, the wands 50 and 52 may be connected to each other, and in this manner a convenient handle which projects upwardly from the floor an even greater distance may be provided. A slight pressure downward on the wands 50 and 52 when they are in the channels 54 and 56 will cause the rear end of the elongated tank 26 to rotate about the rear axle 218 down toward the floor thereby lifting the front end and the caster from the floor so as to make it easier to wheel the vacuum cleaner of the present invention around a home or to push it up an incline, as is apparent by reference to FIG. 1. v

The tool holding and handle assembly 32 also comprises a handle 58 so that the entire vacuum cleaner may be lifted by the handle if desired. The hose holding wall section 33 is constructed with a pair of elongated side walls 60 and 62 which slant slightly outwardly and a pair of semi-cylindrical walls 64 and 66 on the opposite ends of the section 33.

The flexible hose assembly 72, which is coupled to the intake of the vacuum cleaner in FIG. 1, is formed of three parts and may be stored in the hose holding section 33 by wrapping it around the walls 64 and 66 and inside of the side walls 60 and 62 (FIG. 2). The parts of the hose assembly 72 consist of the flexible hose 74, the plastic coupling member 76 which is inserted into the intake opening 78 on the front cap 22 and the tube 84. The hose 74 is held in place by the locking control member 80 which is formed with a semi-circular lower surface (not shown), which engages a corresponding groove (not shown) on the coupling member 76.'When it is desired to remove the hose assembly 72 from the intake aperture 78, the locking control member 80 is raised thereby raising the semicircular locking surface out of the groove on the coupling member 76. The chromium plated curved tube 84 is coupled to the flexible hose 74 by means of a plastic coupling member 86. The curved tube 84 is provided with a stainless steel detent button 87 which resiliently projects into a corresponding aperture on either of the extension wands 50 or 52 when it is mounted on the curved tube 84. Accessory tools also may be affixed to the curved tube using this detent for retention.

The front cap 22 includes a five position suction control mechanism which includes a sliding bleed. valve 88 which may be adjusted so that the suction of the vacuum cleaner may be varied over a large range and the vacuum cleaner may be used under widely different conditions. An air bypass path is provided through the suction control mechanism so that when adjustments of the bleed valve 88 are made they will not be altered substantially by the contents of the bag or by the air resistance of the bag itself.

The front cap 22 also contains an efficiency indicator 90 which is a rubber dome or diaphragm the inside of which is presented to the suction side of the vacuum cleaner. The indicator 90 is constructed of natural rubber, and it will collapse sharply so that it turns itself inside out when the vacuum inside the tank is raised to a high enough level by either a full bag or by a clogging of the tools or wands that are used. Natural rubber or silicone rubber are preferred for the indicator 90 to provide the necessary durability.

The front cap 22 may be opened to allow for replacement of dust bags when the efficiency indicator shows that the dust bag is full. A latch 92 on the upper surface 30 of the tank 26 has a downwardly protruding finger 94 that engages the ledge 9 6 on the top of the front cap 22. When the latch 92 is pulled up the engagement of the finger 94 on the ledge 96 is released and the front cap may be swung downwardly thereby allowing the dust bag to be removed.

The rear end cap 24 houses a cord reel with a plug 104 and a power cord which extends upwardly through a grommet member in the upper surface 108 of the rear end cap 24. The upwardly extending plug 104 eliminates a particularly annoying feature of many cord reel vacuum cleaners which is caused by a tendency of the operator to pull the vacuum cleaner around when the cord is being extended. Since the pulling force on the plug 104 is in a vertical direction, the weight of the vacuum cleaner 20 tends to oppose the pulling force and the vacuum cleaner will not be pulled from it position by the operator.

A large front swivel castor 110 is employed to allow for substantially effortless movability of the cleaner. A pair of large widetrack rear wheels 1 12 which are preferably made of high impact polystyrene and which may have polyvinyl chloride tires 114 are used to provide for easy rolling over either high or low pile carpets. The wheels 112 are, therefore, quiet and non-marring when they roll over bare floors. 7

FIGS. 2 and 3 show the construction and the operation of an embodiment of the stair locking mechanism that may be employed in the vacuum cleaner that has been described with reference to FIG. 1. A more complete description of the vacuum cleaner of FIG. 1 may be found in the co-pending application, Ser. -No. 270,421, which is assigned to the assignee of the present invention;

The stair locking mechanism of the present invention is shown in detail in FIGS. 2 and 3.'In order to mount the stair locking mechanism to a canister vacuum cleaner such as the vacuum cleaner of FIG. 1, two holes 206 and 208 are provided in the housing 201 of the vacuum cleaner. The holes 206 and 208 are above the wheels 112 so that the lock crank 200 may be inserted into these holes and the crank 200 will then be held in place in the housing without the use of further mounting provisions. Holding of the vacuum cleaner on a stairway is accomplished by the lock crank 200, which may be formed of a single solid or hollow bar. However, for ease of assembly, it is preferred that the lock crank 200 be formed in two sections as shown in FIG. 2.

The left-hand section 202 and the right-hand section 204 of the lock crank 200 are inserted through the apertures 206 and 208 in the left and right-hand walls of the housing 201 in the vacuum cleaner, respectively. Both the left-hand section 202 and in the. right-hand section 204 of the lock crank 200 are bent so that lowermost interior sections 210 and 212 of the lock crank 200 are substantially parallel with and adjacent to the bottom 203 of the housing 201. The interior section 210 and interior section 212 are then crimped, or welded or secured by other means, to a sleeve 214 which holds them together thereby completing the structure of the lock crank 200.

The locking arm sections 216 and 218 of the lock crank, which are external of the housing 201, are bent downwardly towards the upper surface of the polyvinyl chloride tires 114 of the wheels 112. In order to improve friction and to prevent damage to the tires 114,

it is preferred that caps 220 and 222 of a. resilient material such as polyvinyl chloride, or other suitable material, be provided over the lowermost ends of sections 216 and 218, respectively. Although the caps 220 and 222 shown in FIGS. 2 and 3 have generally cylindrical shapes with rounded lower ends, the particular shape of the caps 220 and 222 .need not be limited to the shape shown in drawings. 1

The holes 206 and 208, through which the sections 202 and 204 are inserted, are located in the housing above the front portion 224. of the rear wheels 112, as shown in FIG. 3. Slightly forward of the front portion 224 of the rear wheels 112 and of the holes 206 and 208, a disengaging element or resilient nipple 228 is secured in the lower housing surface 203. The nipple 228 has a pair-of enlarged flanges 230 and 232 and a reduced intermediate section 234 which allows the nipple 228 to be compressed and pressed into place in the hole 226, and to be thereby held in place in the hole 226 by the flanges 230 and 232. An upwardly projecting rigid element or stop member 236 is preferably secured to the rear of the nipple 228 in the hole 238. The stop 236 is provided to limit the amount of gripping force of the caps 220 and 222 on the tires 114 to a predetermined maximum force, in order to prevent damage to the tires 114, slippage between the locking caps 220 and 222 and the tire 114 due to over rotation of the lock crank 200, and to provide for more easy release of the locking mechanism. The stop member 236 may be formed with flanges 240 and 242 and reduced intermediate section 244 to hold it in place in the hole 238. The stop member could also be provided by a portion of the housing or some other type of member if desired.

The operation of the stair locking mechanism of the present invention can best be shown by reference to FIG. 3 which shows the bottom portionof the vacuum cleaner and two stairs of a stairway, with the front end of the vacuum cleaner being elevated on the stairway with respect to its rear end. If the operator is merely pulling the vacuum cleaner up the stairway or lowering it down in transport, and does not desire to stop on the stairway to clean it, the locking mechanism can be totally disengaged. The total disengagement of the locking mechanism can also be used on' level ground to prevent the pendulum action from accidentally locking the wheel after a sudden motion or jerk on the vacuum cleaner. This disengagement is achieved by pushing one of the caps 220 and 222 forwardly so that the lowermost sections 210 and 212 of the crank arm 200 are pushed forward against the nipple 228, thereby compressing the nipple 'sufficiently so that the sleeve 214 can slip forward of the nipple 228 to a position where it will be restrained from moving backward when the pressure on the cap is released. The lock crank 200 is then in the position A and the locking mechanism is disengaged, as shown in FIG. 3. In this position, the nipple 228 prevents rearward movement of the lock crank 200 and the caps 220 and 222 thereforeremain suspended away from the wheels 112. The vacuum cleaner may, therefore, be moved forward or rearward, up or down an incline without engagement of the locking mechanism when the lock crank 200 is in position A.

If one of the knobs 220 and 222 are pushed to the rear by the operator, the sleeve 214 may be forced to the rear of the compressible nipple 228. If the front end of the cleaner 20 is now raised, the lock crank 200 will assume position B. In position B, the gravitational forces acting on the lock crank 200 force the locking caps 220 and 222 to rest against the tires 114. The lock crank 200, which is suspended from the housing 201 at the holes 206 and 208, is thus pivoted in a pendulumlike fashion about its suspension points, in accordance with the angle of inclination of the vacuum cleaner with respect to the horizontal and contact between the caps 220 and 222 of the lock crank 200 and the tires 114 will occur whenever the angle of inclination of the vacuum cleaner exceeds some predetermined minimum angle with respect to the horizontal. When the lock crank 200 is in position B, the caps 220 and 222 engage the tires 114, and as the wheel is rotated rearward, friction between the tires 114 and the caps 220 and 222 cause the lock crank 200 to rotate to position C. The rotation from position B to position C is a quick action, jamming movement which causes the locking caps 220 and 222 to compress the tires 114 sufficiently to lock the wheels 112 in place. As a consequence of this jamming action, the wheels may be locked very positively in spite of the light force of the pendulum mechanism which operates the wheel lock. Thus, further rearward rotation of the wheels 112 is prohibited so that the vacuum cleaner-cannot roll backwards down the stairs. If the vacuum cleaner is then pulled in the forward direction, friction between the tires 1 l4 and the locking caps 220 and 222 will cause the lock crank 200 to rotate back to position B. This will allow the wheels 112 to rotate in a forward direction so that the vacuum can be transported up the stairs.

The locking force of the lock crank 200 on the wheel may be varied within the scope of the present invention in accordance with the various available design factors, such as the weight of the lock crank 200, the circumberence of the wheel 112, the materials used in the caps 220 and 222 and the tires 114, the position of the holes 206 and 208, etc. If desired, the locking mechanism may be designed so that when the vacuum cleaner is pulled forward, the clockwise rotation of the wheel 112 will exert sufficient force on the arms 216 and 218 so that they will be totally disengaged automatically from the wheels 112. It is preferred, however, to require the application of a manual force to the caps 220 and 222 before total disengagement of arms 216, 218 andthe wheels 112 can be achieved to assure a greater margin of safety during operation.

Although a particular embodiment of the present invention has been described, it is not intended that the present invention be limited to the particular embodiment illustrated herein since variations and modifications thereof will be apparent within the scope of the present invention to those skilled in the art.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A mechanism for holding a wheeled vehicle on an incline comprising locking means suspended on said vehicle so as to hang in a non-locking position when said vehicle is positioned on a horizontal surface and so as to hang in a locking position when said vehicle is positioned on an incline greater than a predetermined angle with respect to said horizontal surface, said locking means comprising wheel-engaging means which are in rotation-locking engagement with at least one wheel of said vehicle when said locking means is in said locking position and disengaging means mounted on said vehicle for selectively disengaging said locking means, said disengaging means constructed to restrict the movement of said locking means so as to prevent said locking means from assuming said locking position when disengagement of said locking means is desired.

2. The mechanism of claim 1 wherein said disengaging means comprises a resilient element that is constructed to yield sufficientlyto allow for passage of at least a part of said locking means past said disengaging means when a force is applied to said locking means so as to press said locking means against said disengaging means, said disengaging means being constructed such that said locking means is prevented from moving, due to the force of gravity that isexerted on said locking means when said vehicle is positioned on an incline of greater than said predetermined angle with respect to said horizontal surface, into said locking position by said disengaging means.

3. The mechanism of claim 1 further comprising stop means mounted on said vehicle, said stop means being positioned so as to restrict said locking means from engaging said wheels with excessive force.

4. The mechanism of claim 1 for a vehicle having wheels that have at least one resilient tire wherein said wheel-engaging means comprises at least one resilient element which engages a respective tire when said vehicle is to be held on said incline.

5. The mechanism of claim 1 wherein said locking means is a lock crank having an interior section that extends into said vehicle and at least one wheel-engaging exterior section that extends over a respective wheel, said interior section of said lock crank having a section which is positioned at a substantially lower position than any section of said exterior portion of said lock crank.

6. The mechanism of claim 1 wherein said locking means is a lock crank having a first section and a second section, each of said sections having an interior portion that extends into said vehicle and an exterior wheel-engaging portion that extends over a respective wheel, the inner ends of said interior portions of said lock crank being at a substantially lower position than the wheel-engaging outer ends of said exterior portions of said lock crank and a coupling section joining said inner ends of said interior sections.

7. A wheel-locking mechanism for a vehicle having a housing, a pair of wheels mounted on said vehicle and a hole in said housing over each of said wheels, comprising a lock crank having an interior portion which extends through said holes into said housing and at least one exterior portion which extends outwardly of said housing through one of the holes over one of the wheels, said lock crank being suspended in said holes in said housing such that said exterior portions of said lock crank do not engage their respective wheels when said vehicle is positioned on a horizontal surface and such that said exterior portions engage their respective wheels in rotation-locking engagement when said vehicle is positioned on. an incline greater than a predetermined anglewith respect to said horizontal surface.

8. The wheel-locking mechanism of claim 7 wherein said housing has a pair of side walls, said wheels are rear wheels and said holes are located in said side walls such that said exterior portions of said lock crank engage the upper and front portion of their respective wheels when said vehicle is positioned on an incline of greater than said predetermined angle with respect to said horizontal surface so as to prevent said vehicle from rolling backwards down said incline.

9. The wheel-locking mechanism of claim 7 further comprising a resilient disengaging means that is constructed to yield sufficiently to allow for passage of at least a part of said lock crank past said disengaging means when a force is applied to said lock crank so as to press said lock crank against said disengaging means,

said disengaging means being constructed such that said lock crank is prevented from moving, due to the force of gravity that is exerted on said lock crank when said vehicle is positioned on an incline of greater than i said predetermined angle with respect to said horizontal surface, into said locking position by said disengaging means.

10. The wheel-locking mechanism of claim 9 wherein said disengaging means comprises a resilient element that is removably secured to the bottom of said housing of said vehicle.

11. The wheel-locking mechanism of claim 7 having wheels that have resilient tires wherein said wheelengaging means comprises at least one resilient element that is constructed to engage its respective tire.

12. The wheel-locking mechanism-of claim 7 wherein said locking means is a lock crank having an interior section that extends into said housing and at least one wheel-engaging exteriorsection that extends over a respective wheel, said interior section of said lock crank having a section which is positioned at a substantially lower position than any section of said exterior portion of said lock crank.

13. The wheel-locking mechanism of claim 7 wherein said locking means is a lock crank having a first section and a second section, each of said sections having an interior portion that extends into said vehicle and an exterior wheel-engaging portion that extends over a respective wheel, the inner ends of said interior portions of said lock crank being at a substantially lower position that the wheel-engaging outer ends of said exterior portions of said lock crank and a coupling section joining said inner ends of said interior sections.

14. The wheel-locking mechanism of claim 9 wherein said housing has a pair of side walls, said wheels are rear wheels and said holes are located in said side walls such that said exterior portions of said lock' crank engage the upper and front portion of their respective wheels when said vehicleis positioned on an incline of greater than saidpredetermined angle with respect to said horizontal surface so as to prevent said vehicle from rolling backwards down said incline.

15. The wheel-locking mechanism of claim 14 wherein said disengaging means comprises a resilient element that is removably secured to the bottom of housing of said vehicle adjacent the front portion of said rear wheels and slightly forward of said holes in said side walls.

16. A wheel-locking mechanism for a tank type vacuum cleaner having a tank and supporting wheels at one end thereof comprising a pendulum member pivotally supported on said tank and including a wheelengaging portion, said member in the horizontal position of said tank being positioned with said portion out of engagement with said wheels, pivotal movement of said member asa consequence of raising the other end of said tank causing said portion to engage at least one of said wheels, said portion and said member being positioned when engaged with said one wheel to permit rotation in one direction and lock said one wheel against rotation in the other direction.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORPfECTION Patent No. 3. 820.808 Dated .June 28, 1974 Elmer Eugene Bruning, Donald P. Grover, Manfred Schild and Robert William Nickelson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Inventofls) Column 4, line 4 it" should be --its-;

Column 6, line 56 after "means" insert --being--.

Signed and sealed this 29th day of October (SEAL) Attest:

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents F ORM PO-1 050 (10-69) USCOMM-DC 80376-P69 9 U5, GOVIINNINT PRINYINO OFFICE- I959 0- 

1. A mechanism for holding a wheeled vehicle on an incline comprising locking means suspended on said vehicle so as to hang in a non-locking position when said vehicle is positioned on a horizontal surface and so as to hang in a locking position when said vehicle is positioned on an incline greater than a predetermined angle with respect to said horizontal surface, said locking means comprising wheel-engaging means which are in rotation-locking engagement with at least one wheel of said vehicle when said locking means is in said locking position and disengaging means mounted on said vehicle for selectively disengaging said locking means, said disengaging means constructed to restrict the movement of said locking means so as to prevent said locking means from assuming said locking position when disengagement of said locking means is desired.
 2. The mechanism of claim 1 wherein said disengaging means comprises a resilient element that is constructed to yield sufficiently to allow for passage of at least a part of said locking means past said disengaging means when a force is applied to said locking means so as to press said locking means against said disengaging means, said disengaging means being constructed such that said locking means is prevented from moving, due to the force of gravity that is exerted on said locking means when said vehicle is positioned on an incline of greater than said predetermined angle with respect to said horizontal surface, into said locking position by said disengaging means.
 3. The mechanism of claim 1 further comprising stop means mounted on said vehicle, said stop means being positioned so as to restrict said locking means from engaging said wheels with excessive force.
 4. The mechanism of claim 1 for a vehicle having wheels that have at least one resilient tire wherein said wheel-engaging means comprises at least one resilient element which engages a respective tire when said vehicle is to be held on said incline.
 5. The mechanism of claim 1 wherein said locking means is a lock crank having an interior section that extends into said vehicle and at least one wheel-engaging exterior section that extends over a respective wheel, said interior section of said lock crank having a section which is positioned at a substantially lower position than any section of said exterior portion of said lock crank.
 6. The mechanism of claim 1 wherein said locking means is a lock crank having a first section and a second section, each of said sections having an interior portion that extends into said vehicle and an exterior wheel-engaging portion that extends over a respective wheel, the inner ends of said interior portions of said lock crank being at a substantially lower position than the wheel-engaging outer ends of said exterior portions of said lock crank and a coupling section joining said inner ends of said interior sections.
 7. A wheel-locking mechanism for a vehicle having a housing, a pair of wheels mounted on said vehicle and a hole in said housing over each of said wheels, comprising a lock crank having an interior portion which extends through said holes into said housing and at least one exterior portion which extends outwardly of said housing through one of the holes over one of the wheels, said lock crank being suspended in said holes in said housing such that said exterior portions of said lock crank do not engage their respective wheels when said vehicle is positioned on a horizontal surface and such that said exterior portions engage theiR respective wheels in rotation-locking engagement when said vehicle is positioned on an incline greater than a predetermined angle with respect to said horizontal surface.
 8. The wheel-locking mechanism of claim 7 wherein said housing has a pair of side walls, said wheels are rear wheels and said holes are located in said side walls such that said exterior portions of said lock crank engage the upper and front portion of their respective wheels when said vehicle is positioned on an incline of greater than said predetermined angle with respect to said horizontal surface so as to prevent said vehicle from rolling backwards down said incline.
 9. The wheel-locking mechanism of claim 7 further comprising a resilient disengaging means that is constructed to yield sufficiently to allow for passage of at least a part of said lock crank past said disengaging means when a force is applied to said lock crank so as to press said lock crank against said disengaging means, said disengaging means being constructed such that said lock crank is prevented from moving, due to the force of gravity that is exerted on said lock crank when said vehicle is positioned on an incline of greater than said predetermined angle with respect to said horizontal surface, into said locking position by said disengaging means.
 10. The wheel-locking mechanism of claim 9 wherein said disengaging means comprises a resilient element that is removably secured to the bottom of said housing of said vehicle.
 11. The wheel-locking mechanism of claim 7 having wheels that have resilient tires wherein said wheel-engaging means comprises at least one resilient element that is constructed to engage its respective tire.
 12. The wheel-locking mechanism of claim 7 wherein said locking means is a lock crank having an interior section that extends into said housing and at least one wheel-engaging exterior section that extends over a respective wheel, said interior section of said lock crank having a section which is positioned at a substantially lower position than any section of said exterior portion of said lock crank.
 13. The wheel-locking mechanism of claim 7 wherein said locking means is a lock crank having a first section and a second section, each of said sections having an interior portion that extends into said vehicle and an exterior wheel-engaging portion that extends over a respective wheel, the inner ends of said interior portions of said lock crank being at a substantially lower position that the wheel-engaging outer ends of said exterior portions of said lock crank and a coupling section joining said inner ends of said interior sections.
 14. The wheel-locking mechanism of claim 9 wherein said housing has a pair of side walls, said wheels are rear wheels and said holes are located in said side walls such that said exterior portions of said lock crank engage the upper and front portion of their respective wheels when said vehicle is positioned on an incline of greater than said predetermined angle with respect to said horizontal surface so as to prevent said vehicle from rolling backwards down said incline.
 15. The wheel-locking mechanism of claim 14 wherein said disengaging means comprises a resilient element that is removably secured to the bottom of housing of said vehicle adjacent the front portion of said rear wheels and slightly forward of said holes in said side walls.
 16. A wheel-locking mechanism for a tank type vacuum cleaner having a tank and supporting wheels at one end thereof comprising a pendulum member pivotally supported on said tank and including a wheel-engaging portion, said member in the horizontal position of said tank being positioned with said portion out of engagement with said wheels, pivotal movement of said member as a consequence of raising the other end of said tank causing said portion to engage at least one of said wheels, said portion and said member being positioned when engaged with said one wheel to permit rotation in one direction and lock said one wheel againSt rotation in the other direction. 